1. Field of the Invention
The invention relates to tracked land vehicles, particularly unmanned tracked ground vehicles.
2. Description of the Related Art
Unmanned vehicle technology is an extremely important key to possessing a viable, cost effective and life conscientious future fighting force. While, unmanned aerial vehicles have found success in Iraq and Afghanistan, full size unmanned ground vehicles (“UGVs”) have yet to be deployed. With a large percent of war casualties resulting from ground combat and improvised explosive devices (“IEDs”), it is imperative that the armed services strive to employ UGV technology as soon as possible.
Several full size UGVs have been attempted, including the USMC's “Gladiator,” DARPA/ARMY/Carnegie Mellon's “Crusher,” and Lockheed Martin's “Mule.” However, each of them has shortcomings. They will be discussed in turn below using publicly available information.
Gladiator. In 2005, Carnegie Mellon and United Defense Industries were awarded a contract for the development and demonstration of the USMC Gladiator. As a tracked vehicle, the Gladiator is a robust UGV with little to no suspension, a top speed of approximately 10 mph and weight of approximately 10,000 lbs. Much of the Gladiator's performance characteristics are not published but may be surmised through observation. The origin of the chassis is also not public information but closely resembles what is known in the construction industry as a “Skid Steer.” These are slow moving bucket loaders with stationary idler suspension wheels and rubbers tracks coupled to a hydraulic motor planetary gear drive system. These vehicles are built with a solid plate steel chassis making quick and efficient servicing difficult. While highly maneuverable at low speeds most Skid Steers possess no suspension and struggle to break 10 mph. Power train and valve upgrades are commercially available, however are not recommended due to the Skid Steer's inherent instability at mid-high speeds and lack of suspension. While durable, the Gladiator's off-road performance is very limited and may be vulnerable to attack due to its lack of speed. Furthermore, the Gladiator's modularity and serviceability are also limited due to its welded steel plate chassis design. Gladiator weapons systems include but may not limited to a remote turret capable or firing the 7.62 mm gun.
Crusher. Unveiled in 2006 by DARPA/ARMY and Carnegie Mellon, the Crusher is a 6 wheeled, 14,000 lb UGV possessing a research and development price tag of $35 million. With a top speed of 26 mph and a suspension travel of 30 inches, Crusher offers fair mid-speed performance characteristics and obstacle suppression. The chassis comprises of aluminum tubes, titanium substructures, steel plating and was developed ground up for UGV operation. Again, many of the vehicles design and performance characteristics are not public information, but can be surmised through observations of online videos and graphics. It is clear through the videos that Crushers has a capable off-road chassis, especially when considering its weight, although its drive train complexity is clear and comes into question. The Crusher possesses six different electric drive motors coupled with six different planetary gears for each wheel. With no front steering and all six wheels locked in the same plane, Crusher must turn using differential wheel speed. Thus, Crusher must also possess complex drive software and electrical control matrixes. For these reasons, Crusher's productivity, complexity and serviceability are clear weaknesses. Furthermore, possessing six different planetary drive hubs increases the UGVs vulnerability to IEDs and firearms attacks. How will the Crusher perform with one or two of its drive motors or hubs disabled, which can be accomplished by a simple software failure of a well-placed bullet?
Finally, six wheels certainly are an advantage over four wheels in off-road terrain, but still do not compare to tracks. Much of the footage in Crusher's videos is captured on hard terrain. How will the Crusher compare on softer substrate such as swamp, deep mud, or loose sand?
Mule. At approximately 5,000 lbs, the Mule resembles a smaller version of the Crusher and is developed in part by the U.S. Army and Lockheed Martin. It possesses many of the performance characteristics of the Crusher, yet has an active electro-controlled suspension leveling system. While adding a level of ride control, the active electro-controlled suspension leveling system also adds to the Mule's complexity, cost of production, lack of reliability, and combat vulnerability. The total cost of the Mule's research and development is not public but estimated to be in the tens of millions of dollars along with both the Crusher and the Gladiator. Both the Mule and the Crusher are outfitted with a turret system designed to accommodate a 7.62 mm gun, 50 caliber gun, and Javelin missiles.
In view of the foregoing, what is needed is UGV that is at least twice as fast as those of the prior art, lighter, less vulnerable, and more reliable.